Redshift Mk I (New Purchase)

[Konrad]

I often judge a man’s true opinion about a product by wether he spends his own resources on a replacement. Well, I was so impressed at the potential that my first Redshift (a used purchase) demonstrated in only its first dozen or so flight that I purchased a second Redshift. My first Redshift was a prototype and built by the owner in a rush, by his own admission. With the first Redshift I learned a lot about how to assemble one. I hope to put this knowledge to good use on my second Redshift.
The only real issue I had with the design of the Redshift, was the short control horns for the V-tail. I think I have come up with a practical work around to this issue.

Redshift; Used Purchase

As a result of family issues and that the race season is coming to an end I don’t think I’ll be racing any F3F until 2020. During the 2019 season I was using the very economical (read cheap!) and well dated Strega’s. These did what I hoped they would. That is give me a chance to learn what F3F...

forum.alofthobbies.com

There is also an issue with the OEM quality for the Redshift Mk I. This production kit has been inspected by the designer and no gross errors are apparent with this kit. Add to this that I think I can add some durability based on my repair of my damaged Redshift #1 and I confident that my 2nd Redshift will be of great value to me. I’ve been told that there is a Redshift Mk II (Spada) in development with a new OEM that addresses this issue and adds some subtle improvements. Right now with this Covid 19 pandemic I have some time to build a new ship. I didn’t want to wait for the Redshift Mk II (Spada) particularly when I think I have a more than adequate fix for the Redshift Mk I.

Unlike what we see in today's trend towards ballast in the wings, I’m staying with the ballast in the fuselage. As the Redshift Mk I has the fuselage cross section to carry a ballast tube I see no advantage to a wing ballast systems. In fact I see wing ballast as being detrimental as it dampens the roll response resulting in more control drag for any given aileron control rate. I’m also getting rid of the square ballast tube. I favor the round tube for the adoption of 19mm Tungsten crankshaft counter weights.

I will be doing away with the glass servo tray as it fails to carry the nose loads into the fuselage hoop structure. In fact is stops in the middle of the ballast loading window, not good for my type of landings!

I will be using mini X-10 for the flap servo (30mm x 30 mm). These have the same gear train as the full size X10. For space reasons the full size 30mm x 35mm servo won’t fit. Much to my surprise the KST X0-8 withstood my crash landing just fine. So I’ll stick with the KST X0-8 plus V2 for the ailerons.

All the best,
Konrad

 

[Hank GB Z]

Good Luck Konrad

 

[Konrad]

While sloping last week I saw another fuselage fail from what look like an ok landing. The fuselage broke in the area of the loading window.

I just happen to have a fuselage on the bench that shows what I think is happening. That is the servo tray does not extend into the fuselage to benefit from the hoop strength that the oval cross section offers. In fact it often ends somewhere in the length of the ballast loading window. This results in there being an area where there is little or no strength coming from the geometric shape of the fuselage. Basically we end up with a very weak area where all we have is are straight sided webs trying to keep the nose on. This straight side web offers little or no lateral stability, as a result will buckle way too soon.

The fuse on my bench has two other issues in the ballast loading area. First the ballast tube is not being used to try to support across the loading window by being anchored at both ends of the window. Second the ballast window has sharp corners that just want to start a tear into those weak straight sided webs.

Look at this window compared to what I did with my first Redshift. This is why I'm doing away with the servo tray and square ballast tube with my second Redshift.

Redshift; Used Purchase

Ouch! Sorry to learn of this. Looks like some kind of failure not allowing for the flair (turbulance or RF link). Can we see the failure? On my slopes this seems to be a knock against the Aeroic models, that is the guys claim the fuselages fail far too easily (Schwing Corsa 108 and Stormbird) I...

forum.alofthobbies.com

All the best,
Konrad

P.S.
I do like that this ballast tube is closer to the axis of rotation. But I'm not happy about how it was accomplished.

 

[purview]

Yes, be sure that if you get it too strong on this side of the wing, it may fail on the rear end (strega in mind) on rough landings

 

[Konrad]

Yes, all things will break. I'm trying to show how to extend the life of the fuselage. I should be clear the fuselage I saw fail last week was NOT an Aeroic fuselage.

 

[Konrad]

I'm trying to show that good mechanics during assembly is just as important as good design at time of manufacture. I'm trying to show how I gave the ballast window full 360° support with the fuselage. Also putting the ballast tube on the bottom of the fuselage allowed the ballast tube to be bonded for its full length to the bottom of the fuselage.

I'm also showing that I like to set the servo tray to allow for the placement of some fiber cording and an epoxy fillet at the upper corner of the servo tray and fuselage junction. Of note here I laminated the top of the servo tray with kevlar that then ran up the 4mm fuselage side. Prior to doing that I had placed Kevlar cording and epoxy in the upper corner of the fuselage and tray.

Another benefit of the lower tray is that the push rods clear the massive wing joiner without needing a kink.

All the best,
Konrad

 

[Konrad]

Here I'm trying to add some strength to those thin weak unsupported webs.

I added some side support fillers in the way of plywood. I then scalloped these and the glass servo tray that span the ballast window. This was done to allow for a lot of glass cording to be laid down to add continuous fibers across the ballast window tying the servo tray into the fuselage hoop area.

I then added two layers of kevlar to add some more lateral support. I also brought theses up to make an upper arch. Again trying to tie into the fuselage hoop strength.

I think the structure would have been so much stronger had the OEM supplied a servo tray that spanned the ballast window and tied into the fuselage hoop structure. I think this supplied servo tray was setting up unsuspecting customers too fail.


All the best,
Konrad

 

[Konrad]

To try to allow the push rods a free run to the V-tail I've cut them a bit short so as not to interfere with the V-tail structure in the back. It is a lot easier to pass a 2mm wire than it is a 4.5mm carbon tube. Also to add durability I added an aluminum band to try to keep the pultruded rods from splitting.

At the ballast window I've stressed relieved the corners. I also added a 6 mm plywood bulkhead to try to tie the kevlar arch through the ballast tube end to the bottom of the fuselage.

All the best,
Konrad

 

[Konrad]

OK, now that I've explained why I'm doing away with the OEM servo tray, by way of showing how to fix an installation of said servo tray.

My next issue is what to do with the V-tail control arms? On my Redshift I converted the horns to aluminum and used clevises. This gave me 11mm long control arms. On the customer's Redshift I was able to retain the wire horns and with 4mm spherical joints end and ended up with 10mm long control arms. From my heli days I like the spherical joint. But I love the extra 1mm I got with the clevis. So, I'd like to ask what are your experiences with the various style of control arms, particularly wear.

All the best,
Konrad

 

[Konrad]

Ok, all payments have cleared. So I'm free to start hacking away (sorry building) at this bird.

Anybody have any input on the clevis vs spherical joint?

 

[Konrad]

Since this Redshift Mk I has enough fuselage cross section to make the installation of a ballast tube practical I will be using a fuselage mounted ballast system. To minimize the epoxy fill and add strength the carbon ballast tube needs to be brought as close as possible to the bottom of the fuselage. As byproduct of how the fuselage is made there is a step where the nose section is slide into the main fuselage. This adds a lot of hoop strength to the fuselage. But the resultant step will keep the carbon ballast tube from seating fully against the fuselage for most of the ballast tube's length.
You can see with my first redshift that there is a gap around the ballast window that I had to fill with epoxy soaked cotton balls.
If I grind away a bit of the contact corner as shown I can get the carbon ballast tube to lay down a lot closer to the bottom of the fuselage eliminating a lot of the need for lots of epoxy fill. I will still need to have some epoxy fill as I'm not going to cut into the fuselage hoop to eliminate the step, just break the corner

 

[purview]

Nice flying from today, got the time to do a quick video edit to show my funny "Hot summer" thermal catching with 28°C on the bottom and 25°C here at 970m above sea level. The bottom is approximately 500 above sea...

@Konrad sorry for capturing this thread, the Mk1 is a nice plane and is tuff in handling so keep care!

 

[Konrad]

Have I mentioned how much I like the wing on the Redshift?

The high aspect ratio is down right sexy and efficient. But it has one draw back. That is one needs to use thin 8mm aileron servos. I had concerns using servos this small on a large fast 3 meter glider. My main concern was that the small gears would be easily damaged. Having flown and crashed my first Redshift this concern was unfounded. Mainly due to the fact that the ailerons are rigged up for landing and never hit the ground even on tip strikes.
Now the thin wing does present another problem in that with IDS set ups the spoon (surface horn) is very small. This results in backlash and resolution issues with the servo. Here is a classic case where you can't spend too much money on a servo. My first Redshift is using KST X0-8 plus servos to great effect. KST has just come out with the new HS08 servo that looks to be even better (faster).

The great thing about the KST HS08 is that they take the same IDS servo tray as the X0-8. I've learned that with the Redshift the IDS is best with 50mm push rods for the aileron. Note these do not come in the standard X0-8 IDS package. You will want to order the smaller pushrods. (It is looking like the best push rod for the flaps might be 54mm. Again not found in the standard IDS package).

Make sure that there is space to center the servo tray between the servo tray and Sine Wave Spar. (Clean up and glue blobs between the spar cap and wing skins) In my setup I have less than 1mm clearance between the servo tray and spar caps.

Based on my set up with the original Redshift my ailerons move up 28° and down 17°. By my math this means that the center throw is rigged with the ailerons up about 5°. This is where I put the ailerons as I centered the servo tray. (Again it looks like the 50mm push rod is best).

The bad news is that I can only use about 50% of the servo throw. This is another reason to use strong high resolution servos! To get more that 28° up aileron I would need to narrow the wipers. Based on how my first Redshift flies I don't think I need any more than 28° up aileron.

 

[Konrad]

OK, I think I need some help.

This is the 8th set of control surfaces I've torn off of molded wings. The issue as I see it is that there isn't enough flex in the kevlar for the amount of movement I want. With this Redshift I want the flaps to move 110°.
In preparing the wings am I to use a triangle file to relieve the bottom skins? I think the skins are binding and this puts a lot of leverage on the hinge. I didn't want to use a file for fear of cutting the kevlar fibers.

Ailerons aren't such a problem as they have less than 1/2 the control surface movement 30°+.

 

[Doc James Hammond]

OK, I think I need some help.

This is the 8th set of control surfaces I've torn off of molded wings. The issue as I see it is that there isn't enough flex in the kevlar for the amount of movement I want. With this Redshift I want the flaps to move 120°.
In preparing the wings am I to use a triangle file to relieve the bottom skins? I think the skins are binding and this puts a lot of leverage on the hinge. I didn't want to use a file for fear of cutting the kevlar fibers.

Ailerons aren't such a problem as they have less than 1/2 the control surface movement 30°+.

Hi Konrad. You have identified a manufacturing problem that is a tough one. If the bottom skins are cut enough to give really free control surfaces then they may be cut too much.

So How to fix it?

1. We will use thicker Kevlar tape that can be cut into a bit.
2. We will put extra tabs of Kevlar on the 3 end hinge points - fuse/ailerons/flaps/aileron ends - for double reinforcement here to stop propagation.
3. We have made a new programmable cutting machine for control surfaces to eliminate the "hand work" that sometimes can be "heavy hand work" depending on the worker.
4. Although the workers should be omni-capable of doing any of the processes, since we have all new workers now, we are using some specialisation training for very critical jobs.

Doc.

 

[Konrad]

I can't be the only one with this problem. To be honest most of the hinges appear to be fine when I get the ship. They flop 15° + just fine. I think I need to relieve the skin as I drive the surface down towards 90°.

Now if the OEM can cut the skin with a PCB mill that would do wonders.

I'm now having to add the Kevlar hinge doublers myself. Not as good as a wet lay up. But I think better than a silicone repair hinge.

 

[Doc James Hammond]

I can't be the only one with this problem. To be honest most of the hinges appear to be fine when I get the ship. They flop 15° + just fine. I think I need to relieve the skin as I drive the surface down towards 90°.

Now if the OEM can cut the skin with a PCB mill that would do wonders.

I'm now having to add the Kevlar hinge doublers myself. Not as good as a wet lay up. But I think better than a silicone repair hinge.

Hopefully it will disappear with the newer models, Konrad - just one of those things that you find out along the way.

And you are right much better than silicone.

Cheers,

Doc

 

[Konrad]

This isn't a problem unique to Aeroic model. I have this "stressed hinge" issue with all 4 other molded brands. This is particularly acute with the 90° flaps.

I'm leaning towards this being a problem with the way I implement the flaps. I'm also sure it is a weak point in the molded wing process. But others appear to be able to keep their flaps on the wing. On my next model I'll widen the hinge gap with a triangle file for the needed clearance. And add Kevlar reinforcement before the first flight.

In my reading of manuals I haven't read (or understood) if this Kevlar hinge clearance has ever been mentioned. Like I said before I'm concerned about cutting the Kevlar hinging fibers with the file. And then there is the issue of making the hinge line look horrible.

If Aeroic can develop a controlled well defined hinge line with clearance process that would be great! This could be an added sales feature I know I would be willing to pay for.

If anybody is following along the best hinge repair adhesive is 3M 5200 (it is not a silicone).

All the best,

Konrad

 

[Doc James Hammond]

This isn't a problem unique to Aeroic model. I have this "stressed hinge" issue with all 4 other molded brands. This is particularly acute with the 90° flaps.

I'm leaning towards this being a problem with the way I implement the flaps. I'm also sure it is a weak point in the molded wing process. But others appear to be able to keep their flaps on the wing. On my next model I'll widen the hinge gap with a triangle file for the needed clearance. And add Kevlar reinforcement before the first flight.

In my reading of manuals I haven't read (or understood) if this Kevlar hinge clearance has ever been mentioned. Like I said before I'm concerned about cutting the Kevlar hinging fibers with the file. And then there is the issue of making the hinge line look horrible.

If Aeroic can develop a controlled well defined hinge line with clearance process that would be great! This could be an added sales feature I know I would be willing to pay for.

If anybody is following along the best hinge repair adhesive is 3M 5200 (it is not a silicone).

All the best,

Konrad

Hi Konrad - best to be a little careful as if the control surface hinge point gap gets to wide it may cause the surface top gap fairing to catch. Had that happen - one flap down - before but it was not one of my models. By the way I landed the plane fine.

Cheers,

Doc

 

[Konrad]

Yep, too wide is a problem with keeping the control surface aligned. I've had a lot of issues with hug up wipers. This has been traced to delamination of the flap, wing flex, inadequate wiper lead in and I'm sure hinge flex.

At the hinge I hope to keep the gap about 0.15mm to 0.2mm wide, the triangle file cutting the needed clearance in the skin below the Kevlar.